1. Field of the Invention
The present invention relates to a pretreatment agent for a fish food, namely fish and shellfish with which the yield can increase and palate feeling can be kept good, and to a process for pretreating a fish food. More particularly, it relates to a pretreatment agent for a fish food which is effective to significantly increase the yield and to retain palate feeling and good appearance during heating and cooking a fish food, especially frozen ones in a microwave oven, and to a process for pretreating a fish food using said pretreatment agent.
2. Discussion of the Background
When a fish food, especially one once placed in a frozen state is heated and cooked, a remarkable exudation of water, a lowering in the yield and shrinkage of its body occur to result in the deterioration such as hard palate feeling and unfavorable appearance.
As means to solve deterioration of quality, a number of pretreatment agents for a fish food have been hitherto developed. There have been proposed processes wherein a fish food is immersed in an aqueous solution of the respective pretreatment agents as shown below. Various polyphosphates (JP 60-199339 A), sodium chloride and albumen (JP 59-179051 A), sodium chloride and an inorganic salt (JP 06-165634 A), calcined calcium (JP 07-322853 A), organic acid fermenting solution (JP 2000-116340 A), transglutaminase (JP 08-182477 A), and the mixture thereof (JP 08-182477 A, JP 09-98746 A, JP 2001-292733 A and JP 2002-51693 A). There have also been proposed a process for contacting a fish food with a mixture of an organic acid salt, sodium chloride, starch, albumen, etc. (JP 05-15344 A).
Even in these processes, however, when a frozen fish food was subjected to heating for a long time, to repeated heating or to severe heating such as heating in a microwave oven, the exudation of water from one cannot be inhibited sufficiently. Therefore, satisfactory quality of fish food could not be obtained in the appearance and palate feeling, due to shrinkage of its body and its hardened property such as dry product. Also, a pretreatment agent consisting of an aqueous solution containing 1–30% (v/v) of ethanol and 5–25% (w/v) of an organic acid salt has been proposed (JP 2001-252049 A). However, even in this process wherein said aqueous solution is used by itself or in combination with an inorganic salt such as sodium chloride, the intended effect can not be achieved by heating under the severe condition as above-stated whereas a good yield, a good palate feeling and natural quality can be achieved by heating under a relatively moderate condition. Also, as in a pretreatment agent containing polyphosphate as the main ingredient, unnatural transparency appears on fish food after the pretreatment and the palate feeling becomes watery. Furthermore, there are some pretreatment agents to be concerned about the influence on the health. The fish food pretreated with a pretreatment agent containing alkaline calcined calcium and an inorganic salt as the main ingredient is susceptible to getting black after heating owing to the promotion of oxidation in the presence of an alkali. There are many pretreatment agents having other problems than just stated.